Heretofore, silver halide photography has been known as a high-sensitive photographic technique. In this photographic method, the image is recorded on a film or the like through a wet developing process, and when the image is to be reproduced, a silver halide emulsion (silver halide photographic paper or the like) is employed, or the developed film is scanned optically to reproduce the image on a cathode ray tube (hereinafter referred to as "CRT").
There has also been an electrophotographic technique in which a photoconductive layer, which is formed on the electrode, is fully charged by corona charging in the dark and then exposed to large exposure energy to thereby change the exposed areas conductive, and the charge in the exposed areas is decreased, thereby an electrostatic latent image on the surface of the photoconductive layer is formed, and thereafter the toner development process in which an electrically charged toner which is opposite in polarity to (or the same as) the residual electrostatic charge is allowed to develop the latent image. This technique is, however, mainly used for xerographic purpose and cannot generally be used for photographic purpose because of low sensitivity. It is common practice to carry out the toner development immediately after the formation of an electrostatic latent image because the electrostatic charge is decreased in short time.
In TV recording technology, photographic recording is effected with an image pickup tube and image information that is obtained by utilization of semiphotoconductor is taken out in the form of an electric signal, which is then outputted to the CRT in this state, or subjected to video recording by use, for example, of magnetic recording to output the image on the CRT at any desired time.
Although the silver halide photography is superior as a means for storing object images, it needs a wet developing process to form a silver halide image and also requires a complicated optical, electrical or chemical processing for reproducing the image on a hard copy, a soft copy (CRT output), etc.
The electrophotographic technique enables the obtained electrostatic latent image to be made visible even more readiy and speedily than the silver halide photography but it permits the latent image to be stored only for an extremely short period and is inferior to the silver halide photography in terms of the dissociation of the developer, the picture quality and so forth.
The TV recording technology requires line sequential scanning to take out and record an electrical image signal that is obtained through an image pickup tube. The line sequential scanning is effected with an electron beam in an image pickup tube and with a magnetic head in video recording, but the resolution, which depends upon the number of scanning lines, is considerably inferior to planar analog recording such as silver halide photography.
Essentially the same is the case with a TV recording system that utilizes a solid-state imaging device (CCD, for example) in regard to the resolution.
These techniques involve the problems that high-quality and high-resolution image recording requires complicated processing, while simpler processing lacks storage function or involves basic degradation of picture quality.
If a photosensitive member that includes a photoconductive layer having an electrode provided on the front side and an electrostatic information recording medium that includes a charge retaining layer having an electrode provided on the rear side are disposed on an optical axis in opposing relation to each other and exposure is carried out with a voltage being applied between the two electrodes, an electrostatic latent image can be formed on the electrostatic information recording medium in accordance with an incident optical image. This method suffers, however, from the problems that the sensitivity is low, and since the electrostatic potential at the unexposed region is high, the contrast ratio of the exposed region to the unexposed region is low.
It is an object of the present invention to provide a photosensitive member which is highly sensitive and capable of applying information charge to an electrostatic information recording medium with an improved contrast ratio of the exposed region to the unexposed region.